Integrated optical waveguide circuit devices, such as planar waveguides, lightwave optical circuits, and optical devices on planar glass and semiconductor substrates are becoming increasingly important in multi-wavelength transmissions systems, fiber-to-the-home, and optical telecommunications systems.
To function, a light guiding waveguide region in the optical device must be interconnected or pigtailed with a light guiding waveguide region in an optical fiber or another optical device. The interconnection requires low loss, typically less than 0.2 db per connection, environmental reliability against heat and humidity, and cost effectiveness. Achieving a low loss connection requires extremely high precision alignment of the light guiding waveguide regions.
One way to align the waveguide region in planar optical devices with the light guiding region in an optical fiber is by active alignment, wherein the waveguide regions are butted together, the alignment is monitored with an optical monitoring tool, and the abutting waveguide regions are then secured together.
Another approach is passive alignment, which involves aligning the waveguide regions by mechanical means. For example, a planar optical device may be aligned with an array of fibers or another planar device by using a pair of MT type connector devices, fabricated by forming V-grooves on a silicon wafer which support a planar waveguide surrounded by a plastic molded MT type connector plug. The V-grooves are precisely located on the wafer, and the V-grooves support guide pins. The guide pins are positioned to be received by guide holes on an oppositely disposed MT-type connector plug which contains an array of optical fibers. Connection of the two plug ends passively aligns the planar waveguide and the array of fibers. Such prior methods do not provide an economic means to precisely align arrays of optical waveguides with optimized optical coupling.